1. Field of the Invention
The present invention relates to a double locking structure for terminal in electrical connectors which is simple in construction and provides a large locking force without increasing a resistance against the terminal being inserted into a terminal accommodating chamber of a connector housing, thereby reliably preventing the terminal from slipping off from the rear of the connector.
2. Description of the Prior Art
A common method of fixing the terminal in the electrical connector and preventing it from slipping off from the back of the connector is by integrally forming a forwardly extending flexible engagement arm on the inner wall of the terminal accommodating chamber, so that the flexible engagement arm is engaged with the terminal inserted into the terminal accommodating chamber.
However, a single-step flexible engagement arm can provide only a weak locking force, so the terminal may come off. To prevent this, some proposals have been made. For example, the Japanese patent Publication No. Showa 54-24116 proposes a structure in which flexible engagement arms are provided to both side walls of the terminal accommodating chamber so as to hold the terminal from both sides. The Japanese Utility Publication No. Showa 54-44779 discloses a structure in which a leaf-spring-shaped housing lance (flexible engagement arm) formed in the connector housing and a leaf-spring-shaped terminal lance formed on the terminal provide a double locking for the terminal. In these cases, while the housing or terminal lances increase the terminal fixing force, there are drawbacks, such as a large insertion force required to insert the terminal, an increase in the size of the terminal accommodating chamber, and a complex internal structure of the chamber.
Structures intended to provide a double terminal locking without increasing the terminal insertion resistance have been proposed. In the Japanese Utility Model Publication No. Showa 54-28625, for example, a through-hole is provided to the connector housing and a pin is inserted through the hole and engaged with a stepped shoulder portion of the electrical contact of the terminal. The Japanese Utility Model Publication No. Showa 60-31171 discloses a structure in which a terminal retainer portion having projected strips for pressing the terminal and also a locking means is mounted, through a hinge, to the rear part of the housing (on the wire connection side) so that the terminal retainer portion can be opened and closed. These constructions, however, increase the number of parts used in the electrical connector as well as the assembly processes and cost, which in turn increases the size of the housing and complicates the internal structure.
As a means of increasing the terminal fixing force without affecting the terminal insertion resistance and the internal structure, the Japanese Utility Model Preliminary Publication No. Showa 61-7875 discloses a structure in which a lock member is inserted between the flexible engagement arm and the inner wall of the terminal accommodating chamber, to prevent deflection of the flexible engagement arm toward the inner wall thereby providing a secure locking of the terminal.
Even with the lock member inserted between the flexible engagement arm--which engages with the terminal--and the inner wall, the terminal is held by only one engagement projection formed on the flexible engagement arm. This engagement projection is limited in size by the dimensional relationship to the terminal and may be cracked or damaged by a large tension on the connected wire, resulting in the terminal slipping off. Such a connector therefore cannot provide a sufficiently large terminal fixing force.
This invention has been accomplished to eliminate such drawbacks and offer a terminal double-locking structure in electrical connectors which has a simple inner structure of the terminal accommodating chamber, which allows the terminal to be inserted with a small insertion force, and which provides a double locking and large fixing force for the terminal, ensuring a stable electrical connection.